102 The Ottawa Naturalist. [December 



elevation on each side of latter near the central part of the valve. In 

 the upper part of the argillaceous Richmond. 



Raflnesquina alternata (Emmons). Mose of the specimens 

 in the upper part of the argillaceous Richmond are nearly flat (Fig. 9) 

 or are only moderately curved, but specimens with stronger curvature 

 also occur. In the limestone interbedded with the shale on the lake 

 shore, about a mile and a half north of the store of J. B. Stratton, 

 specimens occur in which the strong radiating striae are unusually 

 prominent, suggesting the name Rafinesquina alternata varicosa, 

 var. nov. (Fig. 34). These shells are of medium curvature, the 

 curvature being greatest about 35 millimeters from the beak. 



Strophomena parvula, sp. nov., Figs. 10 A-F. Numerous 

 specimens of a small species of Strophomena occur in the upper parts 

 of the argillaceous Richmond and also in the overlying cherty Rich- 

 mond. These are characterized chiefly by their considerable lateral 

 and short anterior extension. The anterior outline varies from more 

 or less evenly rounded to subtriangular and subnasute. This species 

 evidently belongs to the Strophomena planumbona group. There is 

 nothing characteristic about the. interior of either the brachial or 

 pedicel valve. The surface striations are fine, about 5 or 6 in a width 

 of one millimeter, interrupted at intervals by slightly more prominent 

 striae. This species may be readily distinguished from Rafinesquina 

 breviusculus by the flattening of the brachial valve toward the beak, 

 usually accompanied by a gentle concavity, as in all species of 

 Strophomena. 



Specimens resembling Strophomena huronensis Foerste, from the 

 equivalent of the Waynesville member of the Richmond in Manitoulin 

 island, Ontario, occur occasionally in the upper part of the argillaceous 

 Richmond, accompanied by occasional specimens resembling 

 Strophomena nutans Meek, and much more numerous specimens of 

 Strophomena vetusta (James), Figs. 12 A, B. Strophomena neglecta 

 (James), Fig. 11, is fairly common at the same horizon and occurs 

 in the overlying cherty Richmond. In Strophomena vetusta the 

 radiating striae on the brachial valve are relatively coarse; those on 

 the pedicel valve are very fine and often are crossed by fine irregular 

 concentric wrinkles; along the hinge line both valves are wrinkled 

 more or less perpendicularly; and the muscular area of the pedicel 

 valve is subrhomboidal in outline. In Strophomena neglecta the 

 radiating striae on both valves are fine and subequal in size, the size 

 of the shell is larger, and the muscular area of the pedicel valve is 

 circular and supplied with flabellate markings. In typical Strophomena 

 planodorsata the flattened area occupying the posterior part of the 

 brachial valve forms a larger part of the valve and the muscular area 

 of the pedicel valve is relatively larger. 



